1. Field of the Invention
The present invention relates to an engine controlling apparatus for an automotive vehicle, which may take a fail-safe in a limp-home operation in the case where a throttle controlling system is broken down, and more particularly to an engine controlling apparatus for an automotive vehicle, which may take a safety limp-home operation even if not only a throttle opening degree sensor but also a throttle valve would be broken down.
2. Description of the Related Art
FIG. 5 is a block diagram showing a structure of a conventional engine controlling apparatus for an automotive vehicle disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 5-312079.
In FIG. 5, an engine 1 mounted on the automotive vehicle is composed of a plurality of cylinders and provided with an intake pipe 2 and an exhaust pipe (not shown).
An air flow sensor (AFS) 3 is provided upstream of the intake pipe 2 for detecting an amount of air to be fed to the engine 1 to thereby output an intake air amount signal Qa.
A throttle valve 4 is provided within the intake pipe 2 to be openable/closable for adjusting the intake air amount Qa.
A motor 5 provided on a rotary shaft of the throttle valve 4 constitutes a throttle actuator for opening/closing the throttle valve 4. The throttle valve 4 is connected directly to the rotary shaft of the motor 5 or through a gear (not shown) to the rotary shaft thereof.
A throttle opening degree sensor (TPS) 6 detects an opening degree of the throttle valve 4 to output a throttle opening signal T.
A bypass passage 7 is provided at a part of an intake pipe 2 to bypass between the upstream side and the downstream side of the throttle valve 4.
A bypass valve 8 adjusts an opening degree of the bypass passage 7 for controlling a bypass air amount for, for example, a limp-home control.
An accelerator pedal 9 is operated by a driver. An accelerator opening degree sensor (APS) 10 detects an opening degree of the accelerator pedal 9 to output an accelerator opening degree signal A.
The AFS 3, the TPS and APS 10 constitute a variety of sensors for detecting the operational condition of the engine 1 together with other sensors (not shown) such as a crank angle sensor and a vehicle velocity sensor.
A first ECU 11 composed of a microcomputer outputs control signals for driving various actuators on the basis of the operational condition information signals from the variety of sensors.
The first ECU 11 is provided with an engine controlling means for controlling the engine 1 in accordance with the operational condition and a bypass controlling means for controlling the bypass valve 8.
Also, the first ECU 11 is provided with a throttle breakdown detecting means for detecting a breakdown of a throttle controlling system including the throttle valve 4 and the TPS 6, a throttle power source interrupting means for interrupting the power source supply to the motor 5 in the case where the breakdown is detected in the throttle controlling system, and a predetermined operational condition detecting means for detecting that the operational condition has been shifted to a predetermined operational condition corresponding to the fully closed condition of the throttle valve 4 when the throttle power source interrupting means is in operation.
In this case, only the bypass drive signal D for the bypass valve 8 is shown. However, an injection signal for an injector (not shown) within the engine 1, an ignition signal for an ignition plug (not shown) and the like are included in the control signals to be outputted from the first ECU 11.
Also, a second ECU 12 composed of a microcomputer which cooperates with the first ECU 11 through bidirectional communication lines L and is provided with a throttle controlling means for electrically controlling the motor 5 in response to the accelerator opening degree signal A to thereby output a motor drive signal M.
A battery 13 performs a power supply to each ECU 11, 12 through a main relay 14 and at the same time performs a power supply to the second ECU 12 through a motor controlling relay 15 driven under the control of the main relay 14.
The operation of the conventional engine controlling apparatus for the automotive vehicle shown in FIG. 5 will now be described with reference to a timing chart shown in FIG. 6.
First of all, in a normal operational condition, the engine controlling means within the first ECU 11 calculates control parameters for the engine 1 to perform the fuel injection and the ignition control in response to the operational condition.
The bypass controlling means and the throttle power source interrupting means within the first ECU 11 control the bypass valve 8 of the bypass passage 7 by exchanging the information in cooperation with the second ECU 12 through the communication lines L, and at the same time, control the motor controlling relay 15 that functions as the power source interrupting means.
On the other hand, the throttle controlling means within the second ECU 12 outputs a motor drive signal M in response to the accelerator opening degree A to control the throttle opening degree to a target opening degree To (indicated by one-dot line in FIG. 6).
Namely, the throttle controlling means calculates the target opening degree To of the throttle valve 4 on the basis of the accelerator opening degree A from the APS 10 and the information obtained from the first ECU 11 through the communication lines L to control the motor 5 by the motor drive signal M to adjust the opening degree of the throttle valve 4.
At this time, the throttle controlling means performs the power supply to the motor 5 through the motor controlling relay 15 to perform the feedback control of the throttle opening degree in response to the accelerator opening degree signal A.
In other words, the opening degree deviation between the throttle opening degree signal T and the target opening degree To that is varied in response to the opening degree of the throttle valve 4 is taken to perform the control such that the opening degree deviation becomes zero (T=To).
The operation for shifting to the bypass control in the case where any breakdown occurs in a structural component of the throttle controlling system and the bypass valve 8 of the bypass passage 7 is controlled for the limp-home operation will now be described.
In this case, the case where an earth-short breakdown occurs in the TPS 6 is exemplified.
For example, at time t1, when the earth-short breakdown occurs in the TPS 6 and the throttle opening degree signal T is fixed to zero [V], it is impossible to perform the feedback control of the throttle valve 4 to the target opening degree To. As a result, the program is shifted to the bypass control condition through the bypass passage 7 as the fail-safe function of the vehicle operation.
At this time, the throttle breakdown detecting means within the first ECU 11 drives a timer from the time t1 when the throttle opening degree signal T exhibits a level equal to or less than a predetermined opening degree Tr corresponding to the earth-short level (ground level=0 V). A breakdown flag F is turned on at time t2 after a predetermined time tf has lapsed.
Incidentally, if the breakdown flag F is on immediately after time t1 when the throttle opening degree signal T exhibits 0 V, there is a possibility that the breakdown would be misjudged in the case where there would be the affect of noises or the like. Accordingly, in the case where the condition equal to or less than the predetermined lower limit is continued for the predetermined time period tf, the breakdown flag F is on (i.e., the breakdown judgement).
Thus, the throttle power source interrupting means within the first ECU 11 interrupts the magnetic excitation of the motor controlling relay 15 at the on-time t2 of the breakdown flag F and interrupts the power supply from the second ECU 12 to the motor 5.
Accordingly, there is no torque generated by the motor 5. As a result, the throttle valve 4 is kept at the fully closed condition by a return spring (not shown) provided on the rotary shaft.
Also, the bypass controlling means within the first ECU 11 turns on the bypass drive signal D and opens the bypass valve 8 to feed the bypass intake air amount through the bypass passage 7 to the engine 1.
Accordingly, under the condition that the throttle valve 4 by which the feedback control is disabled is fully closed, the engine 1 is driven with the minimum possible operational ability by the intake air amount through the bypass passage 7 so that the vehicle may be driven in the limp-home mode to the service station.
Incidentally, the breakdown of the motor 5 in the throttle controlling system is detected by, for example, the deviation between the target opening degree To and the actual throttle opening (throttle opening degree signal T), or the relationship between the intake air amount signal Qa and the target opening degree To. In this case, in case of the detection of the breakdown of the motor 5, the opening degree control of the bypass valve 8 in response to the accelerator opening degree signal A is controlled.
Thus, the conventional vehicle engine controlling apparatus interrupts the power supply to the motor 5 in response to the on-operation of the breakdown flag F in the case where the breakdown is detected in the throttle controlling system, and at the same time, performs the limp-home control of the vehicle.
If the breakdown is the simple earth-short breakdown of the TPS 6, there is no problem. However, it is impossible to confirm the condition of the throttle valve 4 (i.e., whether or not the throttle valve 4 is actually fully closed even if the drive of the motor 5 is stopped). Accordingly, the conventional apparatus suffers from the following defect.
For instance, if there is an opening fixed condition (open breakdown) in which the throttle valve 4 is not fully closed even if the drive of the motor 5 is stopped, and if the bypass valve 8 is opened in response to the on-operation of the breakdown flag F, the intake air amount to be fed to the engine 1 is excessive, resulting in difficulty in decelerating or stopping the vehicle.
As described above, according to the conventional vehicle engine controlling apparatus, since the bypass passage 7 is opened irrespective of the breakdown condition in detecting the breakdown of the throttle controlling system, the conventional vehicle suffers from a problem that it is difficult to decelerate or stop the vehicle in case of the open breakdown of the throttle valve 4.